人呼出飞沫核在人体微环境中的沉降机理研究

Deposition of expiratory aerosols in human microenvionment contributes to indirect contact transmission of respiratory diseases. Existing studies provide inadequate knowledge of not only activity-dependent microenvironment but also characteristics of surfaces including skin, mucosa, fabrics and hair. This study aims to reveal the relation between the deposition process and multiple factors that cover features of human activity, surfaces as well as with their boundary layers, aerosols and ventilation. Flow elements in human micronenvironment will be measured at various activity levels, firstly. Temperature, velocity and turbulence profiles will be obtained along human exhalation puffs and plume. Then a series of test will be conducted to compare the deposition of mono-dispersed particles on simple surfaces of rat skin, mucosa and etc. Deposited particles will be sampled by filter paper, while the concentration of particles near the surface will be measured. Correction for using surfaces of breathing thermal manikin will be obtained with consideration of airflow direction, turbulence intensity, surface friction and particle size etc. Full-scale measurements will be conducted with a breathing thermal manikin. Particles will be released from different distances. The weight ratio between deposited particle and the source can directly reveal the deposition patterns. Crucial locations where has a considerable amount of deposition and human touching will be extracted to indicate more effective ventilation rates with air distribution methods, or other engineering control strategies.

人呼出飞沫核在人体微环境中的沉降是导致呼吸道疾病传染的重要环节。目前仍缺乏对人体微环境中的皮肤、粘膜、衣物和头发等各种复杂表面下的沉降机理研究。本项目将以实验测试和CFD数值模拟手段，系统地研究人体体征参数、表面和边界层参数、颗粒物参数和室内通风参数等影响因素对沉降量的影响。首先，建立考虑人体代谢当量下的人体微环境中人呼出气流和表面热羽流的流动特性的数学模型。其次研究颗粒物在不同材料构成的水平或竖直表面的沉降量差别。最后通过全尺寸实验和数值模拟研究通风方式和通风量等因素对人体微环境中人呼出飞沫核在表面上沉降的影响，从而建立典型条件下通风与沉降量之间的定量关系，为实际应用提供参考。

大力改善建筑室内空气质量，降低室内污染已成为国家和社会各界的当前共识，并成为“十三五”期间科技工作的重点领域和前沿课题。本项目围绕污染物在室内环境中的人体微环境中的输送过程进行了系统的研究。分别在：①人呼出飞沫的蒸发和飞沫核形成特性；②人体微环境气流特性；③人际间飞沫和飞沫核的传播特性三方面取得了创新性成果。通过建立人呼出飞沫在室内环境中的运动和蒸发模型， 首次阐明了人呼出飞沫中的带有强吸湿性的金属离子和高分子有机物对不同湿度环境下飞沫核大小的影响机理。系统测量了单人呼吸、咳嗽产生的射流，人体表面热羽流，和近距离多人呼吸和发热共同产生的气流流场特性。明确了人体新陈代谢率，性别，体格，通风方式，人体运动等参数对人体周边气流环境的影响。结合人体微环境气流特性和人呼出飞沫的运动和蒸发模型，系统研究了人际间飞沫和飞沫的传播特性，通过建模量化了病人呼出的飞沫和飞沫核对他人产生的吸入暴露，阐明了人际间距离、室内湿度和室内通风环境成是影响室内飞沫传染风险的最主要因素。基于人呼出飞沫和飞沫核传播模型，首次提出了呼吸道疾病在人际间近距离时的空气传播路径，即病人呼出飞沫中较小的飞沫在迅速蒸发形成飞沫核后，受近距离多人共同形成的人体微环境气流影响，被他人吸入后引起感染。